Wednesday, 1 October 2008

That's the spirit

After painting, I washed my brush in white spirit and wiped it on a paper towel. Later I noticed the towel was covered in flies, that apparently suffered no harm (see Photos). They stayed there for at least an hour. What kind of flies would be attracted to white spirit? I later found more flies drowned in a jar of white spirit some distance away.

White spirits are made of "a mixture of saturated aliphatic and alicyclic C7 to C12 hydrocarbons with a maximum content of 25% of C7 to C12 alkyl aromatic hydrocarbons."[wikipedia]

These hydrocarbons mimic insect hormones which the flies are attracted to for mating purposes.

for a "good time" cover yourself in white spirits! If you like flies that is ;)...[caution] white spirits are a skin irritant and prolonged exposure over many years can also give you nervous system damage.http://en.wikipedia.org/wiki/White_spirit#Toxicity

I should also mention that flies in general LOVE white surfaces covered in black spots.. it will attract them from quite far with or without simulated hormone. They love to jump on the band wagon so to speak so are attracted to clusters of other flies.

If the hormone mimicry explanation is correct, or the black spots explanation, why don't we see this more often? I've had lots of dealings with white spirit over the years and have never seen anything like this.

Is white spirit the same thing in the US and UK?

What species of fly is involved? Have they recently become more common? Is only one sex attracted?

Couldn't it just be the smell of alcohol that attracts them? In nature that usually means rotting fruits, and that is THE place to be for these little flies. Which is also why they cannot stay away from your glass of beer or wine.

I still think the key question is not what attracted the flies - almost certainly something in the smell - but why this phenomenon occurred at all. It is obviously rare enough to merit an entry in this blog. I have never seen such a thing despite plenty of use of white spirit over 50 years in various parts of Europe.

How widespread is this phenomenon? Has its frequency changed recently?

it looks like he wiped it on a paper towel, and left it sitting as pictured. The large surface area probably allowed for a large amount of the spirit to evaporate rapidly and act as an attractant rather than the little evaporation commonly seen from bottles, etc....

I will be interested to know the species of this fly. The juice of sacred basil that is grown in Indian homesteads for religious reasons mainly and for medicinal propose too, is found to atrract a type of flies. But these are not the usual house-flies. Can some one enlighten?M.C.Arunan

Is it possible that it was not the white spirit in itself, which is why we can usually use it without fear of a fly orgy disrupting our work, but something in the paint that was being released as the white spirit broke it down? What kind of paint were you using? Could this be why you're the only person here who's seen this?

I have noticed a similar effect with glo-fuel (similar to a mixture of methylated and white spirits) for RC cars. I spilt some on a sheet of aluminium foil, and when I came back to it the following day, it was covered in dozens of drowned flies. It makes for a handy fly-trap in the summer!

You'll often notice the same effect on the top of tins of other solvents where some of the fluid has leaked and left behind a residue.

This would be related to the annoying phenomenon of small flies landing in my white paint (contains plenty of white spirit) whilst I am painting. Perhaps I could load a piece of white cloth with white spirit to divert them away from my paint.

The following answer has been selected and edited by New Scientist staff

The distinctive wing pattern and green eyes makes these flies easy to identify. They are a fruit fly of the family Tephritidae and the species is Anomoia permunda. The larvae of these flies feed on hawthorn berries.

Insect behaviour is predominantly governed by odour. For example, a female of a species will emit a pheromone to attract a mate. The male reassures the female that he is a true suitor, and not a predator, by emitting another pheromone when he is in close proximity. These chemicals are often common to many insect species, therefore different species will use a mix of chemicals, or confine their activity to different times of the day or year. That way they can use the same pheromone without fear of confusion.

When the female flies of Anomoia permunda search for suitable berries on which to lay their eggs, they do not look at leaf morphology, shape or colour. Instead, they follow a trail of odour, emitted by the hawthorn fruit, to find a suitable egg-laying location. If both fly and host derive a benefit from this odour, as is often the case, the chemical involved is termed an allomone. If only the insect derives a benefit, as seems to be the case with this fly, we call the chemical given off a kairomone.

So why are these flies attracted to white spirit? It is likely that the volatiles given off by white spirit are sufficiently similar to the pheromones emitted by hawthorn berries to fool the flies into landing there. Or perhaps the white spirit volatiles contain components of the pheromones the flies use to find a mate. Either way, the white spirit is luring them in under false pretences.

The following answer has been selected and edited by New Scientist staff

The earlier reply to the question on the strange attraction of white spirit to the fruit fly Anomoia permunda linked their behaviour to the possibility that some substances in the white spirit were similar to those emitted by hawthorn fruit, which attract the flies to lay their eggs there. This reminded me of some work I was party to in South America a few years ago, on the control of the introduced exotic tephritid fruit fly Bactrocera carambolae (commonly known as the star fruit or carambola fruit fly). It showed how such apparently trivial observations can be turned into useful practical measures to control important pest species.

The male of this species is attracted to traces of airborne methyl eugenol, a component of clove oil, which acts as a mating pheromone. In our tests, male flies were attracted to a ring of baits hung in trees around infested carambola fruit orchards. The baits were made from small absorbent strips of board soaked in a mixture of methyl eugenol and the insecticide malathion. When they alighted on the baits, they were rapidly overcome by contact with the insecticide. No native species were affected, nor were the female carambola flies attracted to the baits, so the technique allowed very precisely targeted control of the invading species, and at an astonishingly low cost.

This particular infestation - across Suriname, Guyana and French Guiana - occurred when the fly became capable of using local native fruit species to incubate its larval stage. Fortunately, the work we did ensured it was eliminated very quickly and prevented the spread of the fly across much of tropical South America.

I think the flies in question are possibly fruit flies. The same ones that land in my wifes wine glass when she's supping the vino!So I think the white spirit is giving off the same fumes as cheap red wine.

As well as being attracted by the pheromone-like smell, the flies could be partially disabled by the spirits. This could explain why so many of them were seen on the cloth at once; they weren't very able to fly away.

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